WorksheetsNCCER Electrical 2 Module 10
Total questions: 22
Worksheet time: 11mins
Overloads are often caused by _____.
wires crossing
motors starting
a wire touching a metal frame
a bare conductor contacting a metal tool
Which of the following is TRUE regarding overload current?
Overload current is confined to normal conductive paths.
An overload is the same as a short circuit.
An overload is an unintended current path.
Protective devices must respond to all overloads.
The requirements for overcurrent protection can be found in _____.
NEC Article 240
NEC Article 344
NEC Article 440
NEC Article 517
Circuit breakers and fuses operate in a similar manner as a boiler's _____.
expansion tank
pressure relief valve
heat exchanger
burner
Which of the following is TRUE with regard to circuit breakers?
The interrupting capacity is based on the system load.
The interrupting capacity is the same for each voltage level.
The interrupting capacity is based on its rated voltage.
The interrupting capacity is the same for each frequency.
The frame size of a 20A circuit breaker is _____.
20A
50A
75A
100A
The interrupting rating of an FH-type circuit breaker is _____.
5,000A
10,000A
30,000A
65,000A
Circuits in which the breaker must be highly sensitive to amperage changes should use a(n) _____.
non-automatic circuit breaker
ambient-compensating circuit breaker
standard magnetic breaker
oil circuit breaker
A device that trips when a fault current to ground is 6mA or more is designated by UL as _____.
Class A
Class B
Class H
Class R
The heart is likely to stop when exposed to a current above _____.
5mA
30mA
100mA
200mA
Which of the following is TRUE regarding a dual-element fuse?
It is a single-use only device.
It cannot be used in circuits subject to temporary overloads.
It contains a fuse link connected in series with an overload element.
It should be oversized to prevent nuisance trips.
Type S fuses are available in sizes up to _____.
30A
60A
100A
225A
Which of the following types of drawings helps when sizing fuses for a given application?
Single-line schematic
Large-scale detail
Building elevation drawing
Floor plan
Cartridge fuses used for branch circuit protection must be marked with the ampere rating, interrupting rating (if other than 10,000A), and the _____.
date manufactured
dimensions
expiration
voltage rating
The time-current relationship for a number of overcurrent devices connected in series is
known as _____.
switching
looping
stringing
coordination
Worn motor bearings are most likely to result in a
_____.
temporary overload
sustained overload
short circuit
ground fault
Where in the NEC® would you find information on
circuit breaker applications?
NEC Section 240.85
NEC Section 250.4(A)(1)
NEC Section 310.15
NEC Section 340.12
A 250A fuse has a frame size of _____.
250A
300A
350A
400A
At 300% of its rated current, a circuit breaker rated
at 600V must trip within _____.
7 milliseconds
0.7 seconds
7 seconds
70 seconds
An acceptable fuse combination is a _____.
30A fuse used to protect a non-motor 20A
circuits
10A fuse used to protect a non-motor 20A
circuit
30A non-time-delay fuse used to protect a 15A
motor
45A dual-element fuse used to protect a 15A
motor
When sizing a non-time-delay fuse for a branch
circuit with no motor load, the fuse size must be at
least _____.
125% of the continuous load plus 100% of the
non-continuous load
150% of the continuous load
100% of the continuous load plus 100% of the
non-continuous load
200% of the non-continuous load
Selective coordination is used in complex systems
in order to _____.
shut down the whole system if a fault occurs in
a feeder
ensure that the device nearest any load is faster
than all devices closer to the supply
allow branch circuit faults to trip both feeder and
service overcurrent devices
ensure that the main service fuses have the
shortest opening time for any branch or feeder
fault
